Logging date change for seed dates.

BUG=350415

Review URL: https://codereview.chromium.org/190063007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256299 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/metrics/variations/variations_seed_store.cc

@@ -72,6 +72,44 @@ void RecordVariationSeedEmptyHistogram(VariationSeedEmptyState state) {
                             VARIATIONS_SEED_EMPTY_ENUM_SIZE);
 }
 
+// Note: UMA histogram enum - don't re-order or remove entries.
+enum VariationsSeedDateChangeState {
+  SEED_DATE_NO_OLD_DATE,
+  SEED_DATE_NEW_DATE_OLDER,
+  SEED_DATE_SAME_DAY,
+  SEED_DATE_NEW_DAY,
+  SEED_DATE_ENUM_SIZE,
+};
+
+// Truncates a time to the start of the day in UTC. If given a time representing
+// 2014-03-11 10:18:03.1 UTC, it will return a time representing
+// 2014-03-11 00:00:00.0 UTC.
+base::Time TruncateToUTCDay(const base::Time& time) {
+  base::Time::Exploded exploded;
+  time.UTCExplode(&exploded);
+  exploded.hour = 0;
+  exploded.minute = 0;
+  exploded.second = 0;
+  exploded.millisecond = 0;
+
+  return base::Time::FromUTCExploded(exploded);
+}
+
+VariationsSeedDateChangeState GetSeedDateChangeState(
+    const base::Time& server_seed_date,
+    const base::Time& stored_seed_date) {
+  if (server_seed_date < stored_seed_date)
+    return SEED_DATE_NEW_DATE_OLDER;
+
+  if (TruncateToUTCDay(server_seed_date) !=
+      TruncateToUTCDay(stored_seed_date)) {
+    // The server date is earlier than the stored date, and they are from
+    // different UTC days, so |server_seed_date| is a valid new day.
+    return SEED_DATE_NEW_DAY;
+  }
+  return SEED_DATE_SAME_DAY;
+}
+
 }  // namespace
 
 VariationsSeedStore::VariationsSeedStore(PrefService* local_state)
@@ -158,15 +196,34 @@ bool VariationsSeedStore::StoreSeedData(
   local_state_->ClearPref(prefs::kVariationsSeedHash);
 
   local_state_->SetString(prefs::kVariationsSeed, base64_seed_data);
-  local_state_->SetInt64(prefs::kVariationsSeedDate,
-                         date_fetched.ToInternalValue());
+  UpdateSeedDateAndLogDayChange(date_fetched);
   local_state_->SetString(prefs::kVariationsSeedSignature,
                           base64_seed_signature);
   variations_serial_number_ = seed.serial_number();
 
   return true;
 }
 
+void VariationsSeedStore::UpdateSeedDateAndLogDayChange(
+    const base::Time& server_date_fetched) {
+  VariationsSeedDateChangeState date_change = SEED_DATE_NO_OLD_DATE;
+
+  if (local_state_->HasPrefPath(prefs::kVariationsSeedDate)) {
+    const int64 stored_date_value =
+        local_state_->GetInt64(prefs::kVariationsSeedDate);
+    const base::Time stored_date =
+        base::Time::FromInternalValue(stored_date_value);
+
+    date_change = GetSeedDateChangeState(server_date_fetched, stored_date);
+  }
+
+  UMA_HISTOGRAM_ENUMERATION("Variations.SeedDateChange", date_change,
+                            SEED_DATE_ENUM_SIZE);
+
+  local_state_->SetInt64(prefs::kVariationsSeedDate,
+                         server_date_fetched.ToInternalValue());
+}
+
 // static
 void VariationsSeedStore::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterStringPref(prefs::kVariationsSeed, std::string());

chrome/browser/metrics/variations/variations_seed_store.h

@@ -38,6 +38,10 @@ class VariationsSeedStore {
                      const std::string& base64_seed_signature,
                      const base::Time& date_fetched);
 
+  // Updates |kVariationsSeedDate| and logs when previous date was from a
+  // different day.
+  void UpdateSeedDateAndLogDayChange(const base::Time& server_date_fetched);
+
   // Returns the serial number of the last loaded or stored seed.
   const std::string& variations_serial_number() const {
     return variations_serial_number_;

chrome/browser/metrics/variations/variations_service.cc

@@ -445,8 +445,7 @@ void VariationsService::OnURLFetchComplete(const net::URLFetcher* source) {
       RecordLastFetchTime();
       // Update the seed date value in local state (used for expiry check on
       // next start up), since 304 is a successful response.
-      local_state_->SetInt64(prefs::kVariationsSeedDate,
-                             response_date.ToInternalValue());
+      seed_store_.UpdateSeedDateAndLogDayChange(response_date);
     }
     return;
   }

tools/metrics/histograms/histograms.xml

@@ -23608,6 +23608,16 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Variations.SeedDateChange" enum="VariationsSeedDateChange">
+  <summary>
+    Counts if a response from the variations server is the first response of the
+    day or not. This is counted when a new valid seed or a 304 is received. The
+    date line is computed in UTC and the times being compared are the server
+    time from the server response and the stored server time from the last
+    successful request.
+  </summary>
+</histogram>
+
 <histogram name="Variations.SeedEmpty" enum="VariationsSeedEmpty">
   <summary>
     Records whether the variations seed in local state is empty (does not exist)
@@ -35173,6 +35183,13 @@ other types of suffix sets.
   <int value="5" label="Requests not allowed: disabled by command line"/>
 </enum>
 
+<enum name="VariationsSeedDateChange" type="int">
+  <int value="0" label="No previous date"/>
+  <int value="1" label="New date older than old date"/>
+  <int value="2" label="Same day"/>
+  <int value="3" label="Day changed"/>
+</enum>
+
 <enum name="VariationsSeedEmpty" type="int">
   <int value="0" label="Seed Not Empty"/>
   <int value="1" label="Seed Empty"/>